Published
2007-06-15
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Quantitative Determination of Proteases of Isolated Psychotropic Bacteria in Raw Milk

DOI: https://doi.org/10.22490/24629448.368
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Article (before OJS)
Ana Karina Carrascal Camacho Laboratorio de Microbiología de Alimentos. Departamento de Microbiología, Facultad de Ciencias. Pontificia Universidad Javeriana
Bernardo Clavijo Laboratorio de Microbiología de Alimentos. Departamento de Microbiología, Facultad de Ciencias. Pontificia Universidad Javeriana
Katherine Márquez Laboratorio de Microbiología de Alimentos. Departamento de Microbiología, Facultad de Ciencias. Pontificia Universidad Javeriana
Ing. Balkys E. Quevedo MSC Laboratorio de Microbiología de Alimentos. Departamento de Microbiología, Facultad de Ciencias. Pontificia Universidad Javeriana
Edna Patricia Tascón Peñaranda Laboratorio de Microbiología de Alimentos. Departamento de Microbiología, Facultad de Ciencias. Pontificia Universidad Javeriana
The general use of refrigeration on raw milk has contributed to maintenain its quality, but has induced the selection of psychotropic bacteria which during its growth produces heat-resistant enzymes responsible, in part, for the deterioration of long-life products. This study was designed for the quantification of proteolytic activity in six microorganisms that correspond to Pseudomonas fluorescens R12 y R13, Pseudomonas putida R20, Micrococcus luteus R16, Bacillus circulans R5 y Serratia liquefasciens R4, isolated and characterized of raw milk.

The strains were cultured in milk broth 11% for kinetics profile and the experimental data was adjusted to the Baranyi Model. This Model guaranteed a suitable description of _máx, td y Log UFC. Pseudomonas putida R20 showed the best growing profile with _máx = 0,1066h-1 and td = 6,5023h. Proteolytic activity was determined according to Hübner and it was established that Bacillus circulans R5, in a temperature of 5ºC, produced at the 4th fermentation hour the largest amount of proteases (3,618UP/mL) with the rest of the used strains. Finally, it was established that the temperature with the largest proteolytic activity was 5ºC and, as it increases, it causes a considerable decrease in protease production.